A variety of technologies exist for tracking the direction that a user gazes upon a computer screen, usually referred to as eye-tracking or gaze-tracking. Over the last few years, the hardware and software required to perform such functions has gotten less expensive, more robust, and has been enabled through progressively smaller and smaller embodiments. This trend is expected to continue to the point where gaze-tracking hardware and software may become standard equipment upon personal computers, laptops, PDA, and even cell phones. At the present time, the primary applications of gaze-tracking technology are directed at specialized tools for performing marketing research and other user studies as well as specialized tools for enabling persons with mobility disabilities to interact with computer systems. For example, many applications of gaze-tracking technologies are used to study how people visually explore the information presented on computer screens. These studies, usually performed by marketers and user-interface researchers are geared towards understanding which content on a computer display people spend their time looking at. This is because gaze-tracking technology can determine with a high degree of accuracy which pictures, words, menu items, or even pixels a user is looking at any given moment in time. In a quest to develop optimized web pages and computer driven advertisements, researchers use such gaze-tracking tools to quantify the effectiveness of certain layouts and presentations to grab user attention to desirable content. In the disability field, many applications of gaze-tracking technologies are used to enable individuals who have limited physical mobility to control a computer cursor and/or make other selections within a computer interface by using their eyes as the input control. The gaze-tracking technology determines where the user is looking at controls the cursor to follow their gaze. Often a blink is used to emulate the clicking of a mouse thereby enabling a user to have full cursor control using only their eyes as the input means. For example, a company called EyeTech Digital Systems produces such products for disabled users. Their technology is now small enough and low cost enough to be mounted directly upon a standard laptop and takes up little more physical space than would a standard web cam and a pair of speakers.
A variety of technologies exist for gaze-tracking. These technologies generally employ one or more digital camera aimed at the eyes of the user of a computer system. These technologies sometimes also employ a source of lights, sometimes structured light, such that the reflection of the light off the eyes can be captured by the digital camera and used to determine where on the display screen a user is looking at. For example, an eye tracking device has been developed by the IBM Corporation at its Almaden Research Center and is referred to by the acronym “MAGIC.” This device is mounted proximate to a display screen, in a known positional relationship. When a user is viewing the screen, the IBM eye tracking device determines the point of gaze or focus, with respect to the screen, of the pupils of the user's eyes. Such device generally comprises a camera which acquires successive image frames at a specified rate, such as 30 frames per second. The device further comprises two near infrared time multiplexed light sources, each composed of a set of IR light emitting diodes (LED's) synchronized with the camera frame rate. The system tracks eye focus by detecting the reflection of the emitted light off the user's eyes. Such a process is described in more detail later in this document. One gaze-tracking system for enhancing the usability of portable computing devices that uses such an eye-tracking system is disclosed in pending U.S. Patent Application Publication No. 2003/0038754, entitled “Method and apparatus for gaze responsive text presentation in RSVP display,” which is hereby incorporated by reference. Another gaze-tracking system is disclosed in pending U.S. Patent Publication No. 2002/0180799, entitled “Eye gaze control of dynamic information presentation,” which is also hereby incorporated by reference. This system is directed at controlling the rate of scrolling of a text document based upon where the user is looking. Another gaze-tracking system that has been more recently developed is disclosed in pending U.S. Patent Application Publication No. 2004/0075645, entitled “Gaze tracking system,” which is also hereby incorporated by reference. This system is advantageous over some prior art systems in that it only requires a single camera pointed at the user and does not require calibration and lighting control.
Widespread integration of eye trackers into consumer systems requires that eye trackers be easy to use, affordable, accurate, and less constrained by head and body movements of users. Another gaze-tracking system is disclosed in U.S. Patent Application Publication No. 2005/0175218, entitled “Method and apparatus for calibration-free eye tracking using multiple glints or surface reflections,” which is hereby incorporated by reference. The aforementioned systems and other recent advances in gaze-tracking are expected to increase the robustness and decrease the size and cost of gaze-tracking systems available in consumer markets. As the current trends continues, gaze-tracking systems are expected to soon be commonly available on mainstream consumer products such as personal computers, laptops, PDAs, cell phones, and other devices that include display screens for presenting information to users. With the expected proliferation of gaze-tracking technologies within the user interfaces of mainstream consumer products, there will be substantial opportunities for gaze-responsive software tools that are intended to support more than esoteric research applications and/or very narrow disability populations.
Over recent years significant advances have been made in the design of user interfaces of computing systems enabling easier and more convenient interaction. Current systems are still deficient, however. A significant problem arises for computer users utilizing multi-tasking environments such as Windows where they are very often reading documents while simultaneously performing other functions such as searching for pictures, viewing video, talking with colleagues, or even simply reaching for a cup of coffee. In such situations users often look away from a text document they are reading to perform some other function and then must waste time re-scanning a portion of the document to find their lost place. As people develop multi-tasking work habits, this problem of visually finding a lost place within a text document is becoming an increasing waste of time and effort for users. And as people perform more and more tasks on portable devices, they often must look away from documents they are reading to scan their local environment for they may be walking down the street with a PDA while reading the text document. Current systems are therefore deficient because they fail to help users to find their lost place in a textual document such that they can resume reading without needing to waste significant time re-scanning the text to find where they left off.